CD3 antigen is associated with the T-cell receptor complex on T-cells. Multispecific antigen binding proteins having specificity to CD3 and an antigen of a target cell can trigger the cytotoxic activity of T-cells on target cells. Namely, by multispecific binding of the antigen binding protein to CD3 and to a target cell, e.g. a tumor cell, cell lysis of the target cell may be induced. Antigen binding proteins with a CD3 binding site and their production are known in the art (and described for example in Kipriyanov et al., 1999, Journal of Molecular Biology 293:41-56, Le Gall et al., 2004, Protein Engineering, Design & Selection, 17/4:357-366).
Besides quadroma derived antibodies, a variety of formats of multispecific recombinant antibody fragments have been designed. A particular format of multivalent, and optionally multispecific antibody fragments are named “tandem diabodies” (TandAb®), since their design is based on intermolecular pairing of VH and VL variable domains of two different polypeptides as described for diabodies (Holliger et al., 1993, Proc. Natl. Acad. Sci. USA, 90:6444-6448). The described antibodies are bispecific for a tumor antigen and CD3. In contrast to bivalent scFv-scFv (scFv)2 tandems the tandem diabodies are tetravalent, because they have four antigen-binding sites. The tandem diabodies are devoid of immunoglobulin constant domains. It was reported that the tandem diabodies have advantages such as a high affinity, a higher avidity, lower clearance rates and exhibit a favorable in vitro and in vivo efficiency (Kipriyanov et al. J. Mol. Biol. (1999) 293, 41-56 and Kipriyanov Meth. Mol. Biol. (2009) 562, 177-193).
Such bispecific tandem diabodies can make a bridge between a tumor cell (e.g. B-CLL cell) and a CD3+ T cell of the human immune system, thus permitting killing of the tumour cell. The tight binding of the tumor cell and the T cell induces the destruction of the tumor cell. While such tandem diabodies have proved to be favorable for therapeutic applications, e.g. for therapeutic concepts for the treatment of tumors, there remains a need for improved antigen-binding molecules.
To facilitate toxicology assessment of T cell recruiting multispecific antibody fragments in non-human primates (NHP) during preclinical development, a cross-reactive CD3 binding domain is desirable.
The murine IgG clone SP34 (EMBO J. 1985. 4(2):337-344; J. Immunol. 1986, 137(4):1097-100; J. Exp. Med. 1991, 174:319-326; J. Immunol. 1991, 147(9):3047-52) binds to human and cynomolgus CD3E has been selected for humanization.